1. Field
One or more embodiments of the present invention relate to bleed-out preventing agents, compositions for preventing bleed-out including the same, and methods of preventing bleed-out.
2. Description of the Related Art
Lead frames for packaging semiconductors or printed circuit boards may be subjected to an assembly process in which semiconductor chips and external circuits are connected to form a single semiconductor package, and a die bonding process, a wire bonding process, and a molding process are generally included in the assembly process.
A die bonding process is a process in which a die pad such as a lead frame or printed circuit board and a semiconductor chip are fixed with an adhesive, wherein a die bonding resin (e.g., an epoxy-based resin) is mainly used as the adhesive.
A bleed-out phenomenon may occur in which resins or additives are leached out according to the presence of surface contamination due to organics such as a discoloration inhibitor and a sealing agent, a degree of surface roughness due to plating of a die pad, or physical properties of a die bonding resin used. Bleed-out may decrease die-bonding strength or may cause defects in the subsequent wire bonding process. Also, the bleed-out may cause reliability degradation of a finished semiconductor package.
In a case where a surface of a die pad is coated with silver, Ag2S may be formed on the silver-plated surface of the die pad due to sulfur and oxygen in air to cause discoloration. Thus, this may not only decrease the appearance quality of a product, but may also cause defects in a wire bonding process. In a case where the surface of the die pad is not plated with a noble metal such as gold, silver, and palladium, copper in the die pad may be in contact with oxygen in air to cause surface oxidation. Thus, this may not only decrease the appearance quality of a product, but may also cause defects in a soldering process.